Method of bleaching fibers



Patented May 9, 1933 UNITED STATES search Re PATENT OFFICE HANSKAUFFMANN, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR T0 BUFFALOELECTED-CHEMICAL CO. INC., 0F BUFFALO, NEW YORK METHOD OF BLEACHING-FIBERS No Drawing. Application filed December 10, 1931, Serial No.580,219, and in- Germany October 4, 1930.

The present invention relates to a process of bleaching fibers and moreparticularly to the bleaching of fibers of vegetable origin such ascotton.

The present invention provides a process for bleaching goods in whichthe goods are saturated with an acid hypochlorite solution, thereafterlaid down, washed and subsequently treated with a hot alkaline hydrogenperoxide solution. This process possesses numerous advantages over theolder processes since the goods treated in this manner have a lower costin preliminary treatment, due to the small quantities of bleachingagents required, since the goods treated do not have the same tendencyto decompose hydrogen peroxide solutions which untreated goods possessor which is possessed by goods subjected to other preliminarytreatments. They can therefore, either be bleached with smallerquantities of hydrogen peroxide of a given strength, or conversely theuse of proportionately stronger solutions of hydrogen peroxide ispermitted, which can be used again. In addition, solutions of hydrogenperoxide of higher alkalinities may be used.

Further, goods treated in the manner as outlined herein apparently donot lose in strength or in weight, even over long and extensive periodsof contact with certain of the bleaching materials. It has been foundthat colored stripes, designs, etc., which are woven in the goods do nothave their colors affected appreciably by this process, due to the shortduration of the treating time and therefore the limited time of contactof the colored portions with the bleaching agents. Pre-treatment of thegoods with chlorine efiects a material saving in handling since thenecessity of desizing and boiling is eliminated.

In proceeding in accordance with the present invention unbleached goodsare treated initially with chlorine and subsequently with hydrogenperoxide. The treatment with chlorine may be effected in either of twoways: first, the goods may be wet out and thereafter placed in anatmosphere in contact with chlorine gas or, the goods may be passedthrough water into which a stream of chlorine is being introduced.

It is to be noted, that in either method of treatment with chlorine,contacts of chlorine with the goods should be of short duration, on theorder of a few seconds to several minutes or more. In either case, aftertreatment with chlorine in the presence of moisture, for a time which issuflicient to produce a preliminary effect therein, the goods are washedout and then subjected to the final hydrogen peroxide bleaching process.

It is believed that the elfectiveness of the chlorine is due to thepresence of hydrochloric and hypochlorous acids in equilibrium in thewater solution, and that due to the presence of these chemicals, thepreparation of the goods, as above described, takes place without damagethereto. The preliminary treatment of the goods therefore, is effectedby hypochlorous acid in the presence of an excess of hydrogen ions.

Solutions of hydrochloric and hypochlorous acids may also be prepared inother ways than the method described, as for instance, by acidifying anddiluting ordinary commercial alkaline hypochlorite solutions, as forinstance sodium hypochlorite or by dissolving and acidifying ordinarychloride of lime or bleaching powder. In any case, wherever hydrochloricand hypochlorous acids are produced in solutions, this solution has thespecific effect of preparing goods in a condition quite suitable forbleaching with hydrogen peroxide, since such goods, after treatment andsubsequent water washing exert a substantially slight decomposing actionon hydrogen peroxide.

After subjecting the goods to the preliminary tr-eatment with chlorineand water mixtures, the goods are subsequently washed with water andthereafter treated with a hydrogen peroxide solution. This treatment maybe eflected in apparatus currently in use, as for instance by piling thegoods upon a kier where the goods come in contact with the hot alkalinehydrogen peroxide solution which is caused to circulate in contact withthe goods for a period of from two to six hours or until the goods areproperly bleached.

Hydrogen peroxide solutions may be made up of one gram of caustic soda,eight grams of silicate of soda, two grams of 100% hydrogen peroxide,per liter of water. It has also been found that the concentration ofhydrogen peroxide as well as the concentration of the alkaline materialsmay be substantially increased above the quantity mentioned above, andthe time of contact of the solution with the goods materially decreasedin order to obtain the same bleaching effect. Thus, it has been foundthat a liter of water to which has been added four grams of causticsoda, fourteen grams of silicate of soda and 3.3 grams of 100% hydrogenperoxide would give an excellent bleach in from fifteen to thirtyminutes when circulated in contact with the goods, at a temperatureclose to the boiling point of the solution. The results desired in thevarious bleaching processes will indicate the alkalinity andconcentration of hydrogen peroxide best suited. as at highertemperatures and higher concentrations slightly larger consumptions ofhydrogen peroxide are encountered, while with lower concentrationssmaller consumptions of hydrogen peroxide may be expected but the timeof contact to produce a certain bleach will, of course, be of greaterduration.

After treatment with the circulating hot alkaline hydrogen peroxide, thegoods are washed and rinsed and are found to be in an excellent whitecondition, perfectly bleached and with fibers which are undamaged, andwhich possess substantially their original strength and almost theiroriginal weight. The white obtained is permanent.

It has been found that when using five parts of bleaching solution toone part of goods and good bleaching results are obtained, the hydrogenperoxide loss is about ten percent. Satisfactory bleaching results maybe obtained by this process with a loss of 0.1 to 0.2% of 100% hydrogenperoxide, based on the weight of the goods while bleaching processes .inuse heretofore in which hydrogen peroxide has been used, consumed 0.5 toof 100% hydrogen peroxide per unit of goods.

It is to be noted that various steps of the present process are adaptedfor use in an equipment currently installed and lends itself suitablyfor performance in a continuous system, in contra-distinction to a batchprocess.

hile it is very desirable to use hydrogen peroxide of definite strength,as for instance 100 volume hydrogen peroxide, it is to be understoodthat this reagent may be introduced into the alkaline peroxide solutionby the use of other chemical. compounds. Thus, the solution for thefinal bleach may be prepared from perborate of soda, peroxide of soda,peroxide of barium or zinc, or other chemicals containing active oxygenwhich upon treatment with aqueous solutions produces hydrogen peroxide.

What is claimed is:

1. A process for bleaching cotton fibers and products producedtherefrom, which comprises treating the goods with chlorine water for ashort period of time and thereafter treating the fibers with an alkalinesolution of hydrogen peroxide.

2. A process for bleaching cotton fibers and products produced therefromwhich comprises treating the goods with chlorine of water for a shortperiod of time and thereafter treating the fibers with an alkalinesolution of hydrogen peroxide at an elevated temperature.

3. A process for bleaching cotton fibers and products produced therefromwhich comprises treatin the fibers with chlorine water for a shortperiod of time, and subsequently treating the fibers with an alkalinesolution of hydrogen peroxide which contains at least one gram ofcaustic soda per liter and gyro grams of 100% hydrogen peroxide per HANSKAUFFMANN.

